NCERT Solutions for Class 11 Science Biology Chapter 18 - Body Fluids And Circulation

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Basophils are granulocytes and they secrete histamine, serotonin, heparin, etc. They are involved in inflammatory reactions. 

Hence, the correct answer is option c. 

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The dengue virus binds to platelets and replicates resulting in the multiplication of the infectious virus. The infected platelet cells tend to destroy normal platelets.  It is one of the main causes of the decrease in the platelet count in dengue fever.

Hence, the correct answer is option c. 

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During a cardiac cycle, each ventricle pumps out approximately 70 mL of blood and is called the stroke volume. So, both the ventricles (right and left) pump the same volume of blood during each cardiac cycle. 

Hence, the correct answer is option a. 

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Neural signals sent through the sympathetic nerves (part of the autonomic nervous system) can increase the rate of heartbeat, the strength of ventricular contraction, and cardiac output.

Hence, the correct answer is option b. 

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In ECG, the P-wave represents the electrical excitation (or depolarisation) of the atria, which leads to the contraction of both the atria. The QRS complex represents the depolarisation of the ventricles, which initiates the ventricular contraction. The contraction starts shortly after Q and marks the beginning of the systole. The T-wave represents the return of the ventricles from excited to normal state (repolarisation). Repolarisation of atria is not represented in the ECG.

Hence, the correct answer is option (b). 

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Basophils are granulocytes and secrete histamine, serotonin, heparin, etc. They are involved in inflammatory reactions. 

Hence, the correct answer is option a. 

Disclaimer: The statement "Basophils are granulocytes and secrete histamine, serotonin, heparin, etc, and are involved in inflammatory reactions." is given in NCERT. The solution given in NCERT exemplar is incorrect. The correct answer is option a.

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The ABO grouping is based on the presence or absence of two surface antigens present on the surface of RBCs A and B. ​Antigens are the chemicals that can induce an immune response.  A person having "O" blood group has Anti-A and B in their blood plasma and is called a universal donor. A person having an "AB" blood group has no antibody and they have A and B antigens in their blood plasma. They are called universal recipients. 

Hence, the correct answer is option c. 
 

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The cardiac output of a person is calculated by-
stroke volume x heart rate.

So, the cardiac output of a person having 72 heartbeats per minute and a stroke volume of 50 mL would be -
$72 \mathrm{x} 50 = 3600 \mathrm{mL}$. 

Hence, the correct answer is option b. 

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The human heart is a four-chambered structure. The upper two chambers are the atria and the lower two chambers are the ventricle. Atria are the chambers of the heart that receive blood from different parts of the body. The right atria receive deoxygenated blood from the body organs other than lungs through the vena cava. While the left atria receive oxygenated blood from the lungs through the pulmonary vein. The blood from both the atria flows to the ventricles and valves are present in the atria and ventricle that guard the atrioventricular opening after the blood flows from one chamber to the other. Valves help to prevent the backward flow of the blood. The Sino-atrial node (SAN) is present at the upper right corner of the right atria and it generates the stimulus for opening and closing of the valve as well as for the systole and diastole movement of the heart chambers. The action potential generated by the Sino-atrial node (SAN) moves to the atrioventricular node present at the lower-left corner of the right atria. From the AV node, the action potential is transferred to the Purkinje fibers present in the wall of the Atrio-ventricular septum and is then spread to the cardiac muscles of the heart. So, the whole functioning of the heart is dependent upon the action potential that is generated from the SA node in the atria.

Hence, the correct answer is option b. 

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Plasma is a straw coloured, viscous fluid constituting nearly 55 percent of the blood.  90-92 percent of plasma is water and 6-8 percent is protein such as fibrinogen, globulins, and albumins. 

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a. Plasma without clotting factors is called serum.

b. Neutrophils and monocytes are phagocytic cells.

c. Eosinophils are associated with allergic reactions.

d. Calcium ions play a significant role in clotting.

e. One can determine the heartbeat rate by counting the number of  QRS complexes in an ECG.

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The P-wave represents the electrical excitation (or depolarisation) of the atria, which leads to the contraction of both the atria. The QRS complex represents the depolarisation of the ventricles, which initiates the ventricular contraction. The contraction starts shortly after Q and marks the beginning of the systole. The T-wave represents the return of the ventricles from excited to normal state (repolarisation).

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Hepatic-portal system is the unique vascular connection that exists between the digestive tract and liver.  The hepatic portal vein carries blood from the intestine to the liver before it is delivered to the systemic circulation. 

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a. Angina pectoris- This heart disorder is characterized by acute chest pain due to insufficient oxygen supply to the heart muscles. This disorder occurs in both males and females of any age but it is more common among the middle-aged and elderly. This occurs due to conditions that affect the blood flow. 

b. Hypertension- Increased systolic pressure causes hypertension and is measured 140/90. This leads to heart diseases and also affects vital organs like the brain and kidneys. 

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Atherosclerosis affects the blood vessels that supply blood to the heart muscle. This disorder is caused by the deposition of calcium, fat, cholesterol, and fibrous tissues that make the lumen of arteries narrower.

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a. Purkinje fibres - Purkinje fibres are the conducting fibres that relay the contraction impulses from the AV node to the walls of ventricles. They are present in the ventricular musculature.

b. Bundle of His- They are a mass of specialised fibres that originates from the AV node.

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a. Fibrinogen- Fibrinogens are required for clotting or coagulation of blood.
b. Globulin- They are primarily involved in defense mechanisms of the body. 
c. Neutrophils- Neutrophils are phagocytic cells that destroy foreign organisms entering the body. 
d. Lymphocytes- Lymphocytes are of two major types – ‘B’ and ‘T’ forms and both the types of lymphocytes are responsible for immune responses of the body. 

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If the clotting of blood does not occur then it results in excessive bleeding that leads to death. 

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The normal time duration of the QRS complex is less than or equal to 0.10 sec. The longer QRS complex than 0.10 sec indicates the chances of myocardial infarction (heart attack). 

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a. 

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a. Anaemia- 
It is a medical condition caused when the number of RBCs or haemoglobin concentration becomes lower than normal.
b. Angina Pectoris-
It is a heart disorder and is also called angina. This heart disorder is caused due to insufficient supply of oxygen reaching the heart muscles. It occurs due to a condition that affects the blood flow. It occurs in men and women of any age but commonly occurs in middle-aged and elder individuals. 
c. Atherosclerosis- 
It is also called coronary artery disease (CAD). This heart disorder is caused due to the deposition of calcium, fat, cholesterol, and fibrous tissues that make the lumen of arteries narrower. In this disorder, the blood vessels are affected that supply blood to the heart muscle. 
d. Hypertension- 
It is the term used for blood pressure which is higher than normal (120/80). In this measurement, 120 mm Hg (millimetres of mercury pressure) is the systolic, or pumping, pressure while 80 mm Hg is the diastolic, or resting, pressure. If repeated checks of blood pressure of an individual is 140/90 (140 over 90) or higher and is called hypertension. High blood pressure results in heart diseases that also affects vital organs like brain and kidney.
e. Heart failure- 
It is the state of heart when it is not pumping blood effectively enough to meet the needs of the body. It is also called congestive heart failure because congestion of the lungs is one of the major cause of this disease. 
f. Erythroblastosis foetalis-
It is a condition in which foetal RBCs are destructed due to an incompatibility between the mother (Rh-ve) and foetus (Rh+ve). This can be fatal to the foetus and cause severe anaemia as well as jaundice to the baby.



 

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Lymphatic system is a network of vessels that collects the interstitial fluid (tissue fluid), along with some protein molecules and drains it back into the major veins. Lymph is the fluid present in the lymphatic system. It is a colourless fluid that contains specialized lymphocytes. Functions of lymph are as follows:

1. They are responsible for the immune response of the body.
2. It allows the maturation of lymphocytes and release B and T cells into the lymph.
3. It also acts as an important carrier for nutrients, hormones, etc.
4. Fats are absorbed through lymph in the lacteals present in the intestinal villi.
5. It keeps the tissues and cells moist.

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a. 

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a. RBCs are formed in the red bone marrow in adults and are devoid of the nucleus in most mammals. They are biconcave in shape.

b. The Sino-atrial node (SAN) can generate the maximum number of action potentials, i.e., 70-75 min^–1. They are the patch of nodal tissue present in the right upper corner of the right atrium. They are responsible for initiating and maintaining the rhythmic contractile activity of the heart, therefore called the pacemaker. 

c. Reptiles and amphibians except crocodiles have a three-chambered heart with two atria and a single ventricle while crocodiles have a four-chambered heart with two atria and two ventricles. 

 

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(a) Hypertension:- It is the condition that involves a constant increase in normal blood pressure i.e., $\frac{120}{80}$ mm Hg.
 If the blood pressure of an individual is equal or higher than $\frac{140}{90}$ mm Hg, this condition is called Hypertension.
High blood pressure results in heart diseases and also affects the functioning of vital organs such as brain and kidney.
(b) Coronary Artery Disease:- This disease is also called atherosclerosis. In this condition, blood vessels are affected that supply blood to the heart muscle. It is caused due to the deposition of calcium, fat, cholesterol and fibrous tissues that makes the lumen of arteries narrower.

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